This invention relates generally to a folding knife having a blade which automatically becomes locked once it is moved to an extended position. Fixed blade knives such as sheath knives, are effective cutting instruments, but because of their overall length, they present problems for transport purposes when space is limited. Folding knives address this problem by providing a handle portion with a retractable blade. Folding knives are a popular means for allowing a blade to be conveniently carried by a user, such as in the user""s pocket, toolbox, glove compartment, backpack, etc. Certain folding knives have a blade which may be automatically locked in an open position and then manually unlocked when the blade is to be closed back into the knife""s handle. Folding knives which have a blade which pivots outwardly from the handle and which automatically locks once in the extended position are desirable for safety purposes, since the blade is prevented from closing on the user""s hand or fingers while the user grasps the handle of the knife during use.
Conventional locking means for automatically locking a pivoting blade of a folding knife in the extended position have included an elongated lock bar pivotally connected to the backside of the knife""s handle. An elongated spring, such as a piano wire-type spring, may be used to urge upwardly on the rearward portion of the lock bar to force a locking tab provided on the forward portion of the locking bar into engagement with a notch provided in the tang of the blade. The notch in the tang is presented to the locking tab when the blade is in the extended position. In this type of knife, the locking bar is depressed, rearwardly of its pivot point in the back of the handle, by the user using one hand, against the upward force bearing on the lock bar by the spring, in order to raise the locking tab out of engagement with the notch in the tang. By simultaneously depressing the locking bar in the manner, the user with his or her other hand would then pivot the blade to the retracted position within the knife""s handle.
Potential disadvantages of this locking bar arrangement include the sheer size of the locking bar, which generally extends the length of a major portion of the handle, and also the weight added to the knife by the locking bar. Further, the spring wire, or xe2x80x9cbackspring,xe2x80x9d takes up additional space, which therefore reduces the space allowed for the blade, and, accordingly, becomes a limiting factor for blade size.
Also, because the lock bar must be depressed rearwardly of its pivot point in order to unlock the blade, a recess or relief is generally required in the backside of the knife""s handle in order to allow the user""s thumb to depress the lock bar downwardly within the handle. This necessity of a recess adds another design requirement for the knife and also could provide an opportunity for the user to inadvertently depress the lock bar, such as by squeezing the handle too tightly or in an awkward manner, during use of the knife, which could, in turn, cause the blade to become unlocked during use. Obviously, this could pose safety concerns.
Various folding knives have been patented. For example, U.S. Pat. No. 1,603,914, issued to Hermann, discloses a spring structure connected to the tang of a blade which is used to open the blade. U.S. Pat. No. 4,502,221, issued to Pittman, discloses a locking knife having a release which is pulled upwardly in order to retract the blade. U.S. Pat. No. 5,692,304, issued to Campbell; U.S. Pat. No. 5,685,079, issued to Brothers, et al; and U.S. Pat. No. 4,811,486, issued to Cunningham, disclose locking folding knives having an engagement tab at the top of the handle for engaging a locking notch within the tang of the blade.
U.S. Pat. No. 5,095,624, issued to Ennis, discloses a folding knife having a pivotal toggle mounted for engaging a pin in the blade handle. The toggle is maintained in its locked position by a coil spring mounted in an elongated bore formed in the knife handle.
Accordingly, even in view of the foregoing designs, there still exists a need for an improved folding knife having a blade which automatically locks when moved to the extended position and which can be unlocked with the use of only one hand. A need also exists for a simplified locking mechanism of less weight than prior designs.
It is, therefore, the principal object of this invention to provide a folding knife having an improved blade locking mechanism.
It is another object of the present invention to provide a folding knife having a blade which becomes automatically locked upon the blade being moved to an extended position and which can be unlocked by the user using only one hand.
Another object of the present invention is to provide a folding knife having a blade locking mechanism with improved means for preventing the blade from becoming inadvertently unlocked.
Yet another object of the present invention is to provide a locking folding knife having a locking mechanism of reduced weight.
Still another object of the present invention is to provide a folding knife having a blade locking mechanism of lower profile, or smaller size, which thus allows for a larger blade to be used in the folding knife.
Another object of the present invention is to provide a folding knife having an improved mechanism for maintaining the blade of the knife in the retracted position.
It is another object of the present invention to provide a method of assembling a folding knife and a method of automatically locking a blade thereof upon the blade being moved to an extended position.
Generally, the present invention attempts to address the foregoing objects by providing a folding knife having an elongated handle with a forward end and a rearward end. A blade is attached to the handle, the blade being connected for movement between a retracted position and an extended position with respect to the handle, and the blade defining a tang portion and a first locking profile, such as a projection or a notch.
A locking member is provided having a second locking profile, such as projection (if the first locking profile is a notch) or a notch (if the first locking profile is a projection), the second locking profile being configured to be engageable with the first locking profile when the blade is in the extended position.
A pivotal connector is connected to the handle and to the locking member and allows the locking member to pivot with respect to the handle. The locking member is movable between a locking position, wherein the second locking profile is in locking engagement with the first locking profile for locking the blade in the extended position, and an unlocking position, wherein the blade is movable with respect to the handle.
A spring is connected to the handle and to the locking member, between the second locking profile and the pivotal connector, for urging the second locking profile towards the first locking profile when the blade is in the extended position.
More specifically, the present invention includes the locking member being a bar having a locking projection at one end thereof and the pivotal connector at the other end thereof. The spring, in one preferred embodiment, is a curved wire spring placed in tension, and in another preferred embodiment, a coil spring placed in tension, for pulling the bar towards the blade. Also in a preferred embodiment, the notch is defined in the blade adjacent the tang of the blade.
The present invention also includes a method of constructing the locking folding knife of the present invention and for automatically locking the blade upon the blade being moved to the extended position.